My 18" X-Caliber Barrel - An ongoing review and discussion

[Deputy819]

I think I’ve got the load for the Sierra 120gr Pro Hunters nailed down. Just shot this 5-shot group this morning at 100 yards and it includes the ‘Cold Bore’ shot. I was lucky enough to have 7 lbs of H-4895 from another project that didn’t come to fruition. That seems to be the ticket with the Sierra 120gr Pro Hunters in THIS barrel….which is what you have as well.

[Okie_Poke]

I think I’ve got the load for the Sierra 120gr Pro Hunters nailed down. Just shot this 5-shot group this morning at 100 yards and it includes the ‘Cold Bore’ shot. I was lucky enough to have 7 lbs of H-4895 from another project that didn’t come to fruition. That seems to be the ticket with the Sierra 120gr Pro Hunters in THIS barrel….which is what you have as well.

That will work!

[Okie_Poke]

I didn't get an opportunity to do any more shooting this weekend. However, I did have a little bit of time this afternoon to take some measurements. One of the things nagging me since I confirmed the factory 123 ELDMs are shooting better than my handloads with the same bullet is whether my reloading process is to blame. While that very well could be it, my measurement excercise this afternoon gives me some confidence that is not the likely culprit. I think I just need to find the powder and charge my barrel likes with this bullet.

To provide some context, I'm reloading for my Grendel on a Dillon XL-750 progessive press. I've modified my loading procedure while I'm doing load workup, however, so that I'm really running it kinda like a single stage press with a case feeder and on-press priming. That is, I'm running the brass through one time to resize and prime but not do anything else. Next, I'm charging with powder off the press, measuring every powder charge. Then, I'm seating on the press, feeding the charged cases into the seater station manually. My resizing die is a Redding Type S FL with a bushing; the seater is a Forster Micrometer. The sizing and seating dies are both set up to "float" in an Armanov toolhead.

Because I'm using a progressive press, I thought that was perhaps introducing more variance into my handloads than I realized, even though I'm measuring ever powder charge instead of throwing them. I have several rounds of factory ammo and several rounds of my handloads left from the last batch I tested. So, I decided to measure 10 rounds of each for a few characteristics. I used a headspace comparator to check the consistency of the brass size. I used a bullet comparator to measure the CBTO to check variance in seating depth. And I used a Sinclair concentricity gauge to measure runout of each loaded round.

I've copied a table below showing the results. In sum, my loaded rounds measured at least as good, or better than, the factory rounds. With respect to brass size, both factory and my handloads varied no more than .002." With respect to seating depth, factory ammo varied .007" from min to max and my handloads varied. .004." With respect to runout, factory ammo averaged .005" in TIR, whereas the handloads averaged .003." The factory ammo had one with .008" of runout and another with .010" of runout, while the largest TIR on my handloads was .005."

image.png

I'm not making any claim that any of this really matters a whole lot in the grand scheme of things. Also, I expect I could probably tighten this up a little bit if I did this on my single stage press. Without digging back through old reloading notes, I don't really know how this compares to my best match ammo I load on my single stage. But that doesn't really matter for present purposes because the point of this excercise was to see whether my handloads were better or worse than factory ammo using these metrics. They are at least as good as the factory ammo. So, that suggests to me the issue is elsewhere and I should try turning other knobs before fiddling with my reloading process. I am hoping a change in powder is the ticket.

[Deputy819]

The change in powder worked for me! I was initially running Benchmark powder, but kept getting a first round “flier” with the other 4 shots stacked on top of each other. I knew from previous testing (with other powders) that my seating depth for the 120gr Pro Hunter was good. Ran a powder ladder with H4895 and ended up going slightly above Sierra’s listed max and “BAM”….no more fliers!! Life is good again. 👍

[Okie_Poke]

I still haven't shot again yet. I probably won't get to until next weekend. But I did load up 10 rounds with each of the following powders this afternoon: (1) CFE 223; (2) SW Match; (3) AR COMP; and (4) Lever. I backed off of max or even near-max loads and am generally shooting for around 2450 fps with 123 ELDMs. I'll report when I do that shooting.

In the meantime, I was curious how the external measurements of my 6.5 Grendel rounds compared to the handloads for my 6.5 Creedmoor that I loaded on my single stage press. So, I measured 10 of my Creedmoor handloads this afternoon using the same metrics as I did for the Grendel factory ammo and handloads previously. Chart below. Unsurprisingly, the ammo loaded on the single stage is more consistent with respect to these exterior metrics (which may or may not actually matter to practical accuracy . . . ). Both the Grendel and the Creedmoor loads used ELDM bullets, so i'm not comparing Hornady bullets in one cartridge to Berger or Sierra bullets in the other. My Creedmoor loads do get Lapual brass instead of Hornady brass, though I don't know how much that would matter to these measurements. In any event, I have no doubt I could tighten up the external consistency of my Grendel loads by switching back to the single stage, but I'm playing with powder first. While I think variations in these external measurements could affect accuracy in some rifle systems, I consider them to be a pretty small "knob" at the moment and likely lost in the noise of other things. I'm just sharing because I was curious to see the data compared and thought others might be as well.

image.png

[Bonas]

In my experience, Hornady 123 ELDM is very accurate. You might just be chasing a load that's already optimal for your barrel. My best handloads for that bullet only marginally outperform factory, accuracy wise. That's with 27 or 27.5 grains of H335. I have not produced a more accurate load than factory with Benchmark. It's excellent factory ammo.

I wouldn't get too worked up about not being able to load a more accurate round than factory with that bullet. It's premium ammo, after all. Assuming you should do significantly better than Hornady does by switching powders and charges around with the same bullet might be a flawed assumption. If you're dissatisfied with the factory load's performance, maybe switch up bullets signficantly too. I'm not seeing a whole lot of benefit to putting in a lot of time and money trying to beat what's generally recognized as the most accurate factory ammo available by only allowing yourself powder as the variable.

Since it seems like your practical goal is developing a load for your matches, maybe think about what accuracy you need from the bench to hit your personal match potential. For me, that's about .8 moa. For anything below that, for me, the signal of the marginal accuracy gains gets lost in the noise of match conditions. Chasing groups smaller than that isn't worth it, for me. I'd consider forgetting about external case dimensions, standard deviations, etc., and focus on accuracy. If the rifle doesn't shoot Hornady ELDM factory ammo as accurately as you need it to, maybe try a completely different bullet like a 107 grain Match King or similar. If that's still not getting what you need, that barrel might have to be replaced. If Hornady Black shoots 1.2 moa or so, I don't see you getting much below 1 moa, if that even, staying in thr 120 grain weight class.

For what it's worth, I can squeeze sub-.70 moa five shot groups out of my best Grendel barrel with a couple of loads, but it shoots most loads in that 1.5 moa range, just, like pretty much every barrel out there. I think things people post on the internet have created some unrealistic accuracy expectations for ARs. These aren't F-class rifles.

[Deputy819]

In my experience, Hornady 123 ELDM is very accurate. You might just be chasing a load that's already optimal for your barrel. My best handloads for that bullet only marginally outperform factory, accuracy wise. That's with 27 or 27.5 grains of H335. I have not produced a more accurate load than factory with Benchmark. It's excellent factory ammo.

I wouldn't get too worked up about not being able to load a more accurate round than factory with that bullet. It's premium ammo, after all. Assuming you should do significantly better than Hornady does by switching powders and charges around with the same bullet might be a flawed assumption. If you're dissatisfied with the factory load's performance, maybe switch up bullets signficantly too. I'm not seeing a whole lot of benefit to putting in a lot of time and money trying to beat what's generally recognized as the most accurate factory ammo available by only allowing yourself powder as the variable.

Since it seems like your practical goal is developing a load for your matches, maybe think about what accuracy you need from the bench to hit your personal match potential. For me, that's about .8 moa. For anything below that, for me, the signal of the marginal accuracy gains gets lost in the noise of match conditions. Chasing groups smaller than that isn't worth it, for me. I'd consider forgetting about external case dimensions, standard deviations, etc., and focus on accuracy. If the rifle doesn't shoot Hornady ELDM factory ammo as accurately as you need it to, maybe try a completely different bullet like a 107 grain Match King or similar. If that's still not getting what you need, that barrel might have to be replaced. If Hornady Black shoots 1.2 moa or so, I don't see you getting much below 1 moa, if that even, staying in thr 120 grain weight class.

For what it's worth, I can squeeze sub-.70 moa five shot groups out of my best Grendel barrel with a couple of loads, but it shoots most loads in that 1.5 moa range, just, like pretty much every barrel out there. I think things people post on the internet have created some unrealistic accuracy expectations for ARs. These aren't F-class rifles.

Sometimes this is true, but plenty of matches at Camp Perry have been won with AR-10/AR-15 type rifles. Sure, they are “match grade” setups, but with proper load development (and the right equipment) these rifles can be made to shoot pretty darn good….and 1/2 moa is not out of the question.

[Okie_Poke]

In my experience, Hornady 123 ELDM is very accurate. You might just be chasing a load that's already optimal for your barrel. My best handloads for that bullet only marginally outperform factory, accuracy wise. That's with 27 or 27.5 grains of H335. I have not produced a more accurate load than factory with Benchmark. It's excellent factory ammo.

I wouldn't get too worked up about not being able to load a more accurate round than factory with that bullet. It's premium ammo, after all. Assuming you should do significantly better than Hornady does by switching powders and charges around with the same bullet might be a flawed assumption. If you're dissatisfied with the factory load's performance, maybe switch up bullets signficantly too. I'm not seeing a whole lot of benefit to putting in a lot of time and money trying to beat what's generally recognized as the most accurate factory ammo available by only allowing yourself powder as the variable.

Since it seems like your practical goal is developing a load for your matches, maybe think about what accuracy you need from the bench to hit your personal match potential. For me, that's about .8 moa. For anything below that, for me, the signal of the marginal accuracy gains gets lost in the noise of match conditions. Chasing groups smaller than that isn't worth it, for me. I'd consider forgetting about external case dimensions, standard deviations, etc., and focus on accuracy. If the rifle doesn't shoot Hornady ELDM factory ammo as accurately as you need it to, maybe try a completely different bullet like a 107 grain Match King or similar. If that's still not getting what you need, that barrel might have to be replaced. If Hornady Black shoots 1.2 moa or so, I don't see you getting much below 1 moa, if that even, staying in thr 120 grain weight class.

For what it's worth, I can squeeze sub-.70 moa five shot groups out of my best Grendel barrel with a couple of loads, but it shoots most loads in that 1.5 moa range, just, like pretty much every barrel out there. I think things people post on the internet have created some unrealistic accuracy expectations for ARs. These aren't F-class rifles.

Thanks for posting. I am mindful of a lot of this. I am not dissatisfied with the accuracy of the Hornady Black factory ammo per se. It shoots just fine for matches I shoot in. What is frustrating me is that it's more consistent so far than my handloads---a state of affairs I can't really tolerate. I know the Hornady stuff is pretty good ammo, but I'm weighing every powder charge, using quality dies, and using brass sorted by lot. I should be able to beat it or, at a minimum, match it.

I agree that switching bullets is usually a "bigger knob" for dialing in a load than switching powders. I do have a few additional bullets to try, though all of them are in the 120 grain weight class. This barrel has a rifle length gas system because I intend to shoot that weight class of bullets. That may have been stupid on my part in hindsight, but oh well. I'm not saying I won't try a lighter bullet to see if I can get it to work, but I do want to stick with the 120-grain class bullets in general. I like the Hornady ELDM because it's easy to come by and relatively cheaper than some other match bullets.

In terms of what my accuracy goal is, I don't necessarily have one. A solid 1.2 MOA barrel will work for what I do. But . . I'll admit I was hoping this custom barrel would make my AR shoot like my newer factory bolt guns---in that .75 - .80 average range you mentioned.

Finally, I quite agree the extenal dimensions I was measuring and charting for a couple of posts are of secondary importance at best. I don't spend much time worrying about such things, except that I still need to get back to the range to test what I have loaded up. It's easier to find time to measure things at my bench than it is to drive to the range and shoot, so I was measuring things I was curious about when I couldn't get to the range. Mostly for peace of mind to ensure my reloading process wasn't introducing some wild amount of variance I was unaware of. I posted the results of that more for journalling and informational purposes than anything.

Due to kids and life in general, I still haven't found a good day to get back to the range to test any of this. Doesn't look like it's happening this weekend either, regrettably.

[Bonas]

OP, why do you think the length of your gas system will affect the weight class of bullets your barrel will shoot well? I've never heard of that connection before.

[Okie_Poke]

OP, why do you think the length of your gas system will affect the weight class of bullets your barrel will shoot well? I've never heard of that connection before.

It's my understanding the lighter weight bullets may or may not have trouble cycling the bolt in a rifle length gas system on an 18" barrel. That is why I understand Precision Firearms, Odin, and some others to use "intermediate" length gas systems (between medium and rifle length) for 18" barreled Grendels. I have not tested this in my rifle. But, I have an adjustable gas block and and with 123s and no suppressor, the gas block needs to be nearly fully open in order to cycle reliably, depending on the powder.

I finally made it back to the range today. It was a beautiful morning. About 70 degrees with virtually no wind. A rare day in Oklahoma. I was working on load development for both my 6.5 Creedmoor target rifle and this 6.5 Grendel. Grendel results are below. All shot at 100 yards over Xero chronograph. All bullets are 123 ELDM. I had 10 rounds of each load, which I shot in two 5-shot groups but computed velocity metrics across all 10. I measured each group and then determined what the group size would ahve been if I had shot all 10 rounds of each load in a single group. I started with a clean bore and shot them in the order shown below.

Load	1st Group	2nd Group	All 10 Shots	Avg. Vel.	SD Vel.
Factory Black	1.73	2.48	2.48	2466	18.7
CFE 223	1.35	2.50	2.50	2480	15.8
SW Match	2.49	1.97	2.49	2420	18.9
AR COMP	1.30	1.39	2.18	2406	7.4
LeveRevolution	1.80	1.12	1.80	2376	18.8
Benchmark	1.32	0.92	2.16	2364	16.4

I am coming to the conlcusion that this rifle simply has more variability in group size than any other I've paid this much attention to. Factory ammo is out of the same box as the last time out. The Benchmark load is likewise from the same reloading run as the last time. I guess it really doesn't matter which load it is, sometimes it's going to shoot 1 MOA and sometimes it's going to shoot 2.5 MOA. But for 10 shots, it's looking at 2-2.5 MOA pretty consistently. Weird.

I could get more speed out of all of these powders except for Benchmark. But I think I've seen enough with this bullet. Time to try some different bullets and see how if I can get something to do consistently better than this.

[Former Cav]

I have had troubles also. With 123 Hornady bullets, SST and ELD's the BEST group I can get is with what is NOT recommended because you can't get enough powder in the case at a 2.260 OAL
That is 27.8 grains of Varget, in either Hornady (once fired by me) or New Starline brass using BR4 primers and the above mentioned Hornady bullets.
The speed is SLOW, between 2350-2450 roughly through my Lab Radar unit and also a 35P Oehler chronograph. 13/16 of an inch, 5 round group.
I GAVE up on the Hornady and Sierra 123 Bullets, and am now working on 108 Grain Scenar Lupua bullets because that is what I could buy. I got a load from Dianne (elsewhere on this site) and that load is 5 rounds into LESS then a dime in total diameter. SPEED is SLOW though. That is with Ramshot TAC Powder.

3 LOADS… Mar 28, 2024 (posted elsewhere) The RAC loads were provided by Dianne but with her much heavier 123 bullets!
FACTORY NEMO 120 Gr FMJ BT
H 2596 Low 2515 Avg 2567 Ext Sprd 81 SD 32.8 Not that tight of a group either
TAC by Ramshot powder 27.8 and 27.2 108 Gr Scenar LUpua bullet
27.2 Gr TAC H 2467 L 2336 AVG 2401 Ext SPRD 131 SD 92 cover 4 with a Quarter last one opened up
27.7 Gr TAC H 2452 L 2425 AVG 2438 Ext Sprd 26 SD 13.1 ß all 5 bullets you could cover with a dime!
2.221 overall length. CCI 41 starline brass 2^nd firing cut to 1.510 Palmetto armory rifle w/ 1 in 8 twist SS
Timney Trigger drop in 3 pound pull

[Bonas]

It might be worthwhile to put a different scope/mount combo known to perform well on the rifle to see if anything changes. I've had two instances where I spent a lot of time and ammo chasing an inconsistent "barrel" problem that turned out to be a minor problem with the mount, in one case, and the parallax adjustment on a scope in another. Neither problem could be definitively tied to the optic until after switching it and having the problem go away,

[Okie_Poke]

It might be worthwhile to put a different scope/mount combo known to perform well on the rifle to see if anything changes. I've had two instances where I spent a lot of time and ammo chasing an inconsistent "barrel" problem that turned out to be a minor problem with the mount, in one case, and the parallax adjustment on a scope in another. Neither problem could be definitively tied to the optic until after switching it and having the problem go away,

This is a worthwhile thought. Thank you. If I had a spare scope and mount of equal quality to swap out right away, I would do that---but I don't. Also, while the groups were larger than expected, they all tended to center around the same POI (about an MOA right of center). That's not definitive, but it's a data point. So I'm probably going to do another test with a few different bullets first. But I've got plans on another scope anyway, so I might just have to move that and a new AR mount up the priority list. I would sure like it to be something simple like that I can replace, even if scopes aren't exactly inexpensive.

Bullets that are in line to be tested: 123 Lapua Scenar, 120 Match Burner, 120 SMK. I'm probably also going to test a 130 Berger AR Hybrid. I haven't settled on my testing protocol just yet,

[grayfox]

Sorry I've been tied up and only now got a chance to read this on through. I'll confess that the sst has not been stellar for me. I can get the Eldm to shoot, most of the time in a 20" lilja and using Ar comp. 27.8-28.4 depending on how fast the particular lot is. (The last 2-3 AR comp lots# had a larger delta than I was used to, in powder deltas, but it's an o-well, you just adjust and go on).
But.
I did see back in your load reports that you had a couple sets where MV was 2429-2449 with single digit sd's (groups 20-21 I believe). I don't know how many shots were in them, but you might have something there and just not realize. OAL setting could be ruining your target group.
My next step after finding a load close to my node, with the "small" sd's, is to test for OAL. Take your #20 and #21 load sets, and load three groups of them, 4-5 per group, at those powder charges. the only thing to vary is to do one at your original oal, then one group 0.010" shorter and one 0.010" longer. See if one or the other has a better group size on the target. The chrony is not necessary in this step. What I've been finding is that if I first find my MV, then tweak for OAL, this can alter the bullet's exit-timing enough that the group shrinks or enlarges, from set to set. Basically identical MV's however.
I know factory Hornady for the 123 sst or eldm (forget which one) is ~2.245, but you can try them usually out to 2.275 in an AR mag. The PRS blogs that I follow have a series on bullet seating length, and for them PRS-style, not always the teeniest-tiniest group but one that stays tiny for 150-200 rounds (I like that rather than "chasing the lands")... well their range has been 0.060-0.100 off the lands. I don't think they mean specialty pills like the long Bergers, but for more normal ones like we tend to shoot.

I'll mention a couple more things that helped me, and they may help you too. One, is I switched from Hornady brass to Starline. Hornady just seemed to have more variances and switching has seemed to help - the recipe will be slightly different for starlines b/c a slightly different case volume, but it's been ok. 2, I would check your primer, use the cci 450 if you can. I know, I know, the others are available too, and they do work, but the 450's seem to be the best ones I've found for the AR-grendel. For bolt action GR, I use the federal 205 match ones... just a sidenote. Oh, one more thing, using that Lee factory crimp to put a slight crimp on bullets for the AR, also helps keep them from growing when slammed in by the bcg... just 2 or 3 cents' worth to think about.

Yes, we all in hindsight would maybe go back to spend the bucks for a premium barrel (I did finally with my lilja barrel but there was basically no wait, from the lilja website), but if you have a pretty good one, it's hard to give it up. I still do all these things for my lilja too. Actually for all my calibers pretty much.